The invention relates to a method of inspecting gears during their manufacture in a gear cutting machine.
In addition to numerous inspection criteria, one of the most important is the determination of the dimension over balls since a decision can be made by means of the dimension over balls whether the gear produced is a good part or a reject. The check of the dimension over balls and, optionally, a machine correction associated therewith are an absolute necessity for a reliable production. The determination of the dimension over balls is standardized by DIN 3960. It is a diametric test dimension for the tooth thickness.
The dimension over balls of gears is checked randomly in production. If the inspection level is increased, i.e. if the number of workpieces to be inspected is increased, the metrological and time efforts, and naturally also the costs associated therewith, increase. A number of measuring systems are generally available for the determination of the dimension over balls, with the spectrum usual in practice ranging from simple hand measuring instruments with micrometer screws to automated measuring systems in and on the machine and to 3D gear cutting measuring machines in air-conditioned measuring rooms. On a corresponding determination of the dimension over balls, the gear to be inspected must therefore in each case be removed from the gear cutting machine and measured in the measuring room before any corrections required can be made to the setting of the gear cutting machine.
If a corresponding deviation of the dimension over balls was found in a measured workpiece, it is possible in commercial gear cutting machines to exactly achieve the dimension over balls by corresponding setting parameters or machining parameters on individual workpieces. Furthermore, most machines provide a manual or automatic correction function to react to fluctuations in dimension and thus to keep the process as stable as possible. Primarily the thermal behavior of the machines and the tool wear are to be named as the causes for the fluctuations in dimension and/or the deviations.
The following problems result from the aforesaid procedure: on a measurement of the dimension over balls in an air-conditioned measuring room especially provided for this purpose, the problem arises that the measured result obtained cannot be traced back close to production. A long reaction time is hereby caused for the necessary corrective action. The changed clamping situation may result in measuring errors in grinding/milling and in measurement. If the gear is measured using sensors or styluses, the tool wear is not taken into account and, ultimately, tool changes due to dressing processes of the tool are also not exactly determined and thus enter into the measured result, and thus into the dimensional correction, as an error.